The purpose of this project is to examine the stress response of preterm infants to certain routine nursing procedures in the Neonatal Intensive Care Unit (NICU). The underlying premise is that given the same medical condition, there are individual differences among preterm infants in their response to the routine procedures of neonatal intensive care. These individual differences are reflected in infant baseline behavioral and physiological patterning. Individual differences will affect response to stressful and beneficial nursing procedures and subsequent behavioral organization at term age as reflected by performance on the Brazelton Neonatal Behavioral Assessment Scale (BNBAS). The baseline differences in patterning can potentially discriminate those infants most likely to be negatively affected by the stressful environment of the NICU, thus allowing clinicians to intervene to reduce stress. This project will examine the preterm infant's immediate response on physiological and behavioral levels to four routine nursing procedures, heelprick, turning, nonnutritive sucking, and stroking. Examining the relationship between the immediate response and behavioral and physiological organization at discharge can provide further information not only about the effect of stressors in the NICU environment but also about individual differences in preterm infants' response patterns. This project will study 100 preterm infants of similar post- conceptional age and medical status residing in a level three NICU. Each infant will be studied for baseline values and during four nursing care procedures. All procedures will be those routinely carried out in the NICU. Detailed behavioral and physiological data will be collected prior to, during, and after the procedure by assessing activity, state organization, oxygen saturation, salivary cortisol, and autonomic patterning. At the time of discharge, behavioral organization will be assessed using the BNBAS and a final physiological and behavioral baseline recording.